The goal of this project is to produce Volume III of the Atlas of Steroid Structure. This volume will contain crystallographically determined three-dimensional structures of five classes of steroids which have functions very different from those included in Volumes I and II. The classes to be covered are cholestanes, cholanes, ergostanes, lanostanes, cardenolides; and include membrane constituents, bile acids, hormones such as vitamin D, and cardioactive compounds. As in previous volumes data presentation will be designed to foster easy assimilation and utilization of this information by endocrinologists, medicinal chemists, biophysicists and pharmacologists interested in the molecular level action of biomedically active molecules. The 1200 data pages of the first two volumes of the Atlas include an exhaustive tabulation of molecular geometry and over 3000 ink drawings illustrating the most significant intramolecular and intermolecular structural features of 302 estranes, andostanes, and pregnanes including many of the most active steroid hormones. The Atlas will facilitate comparative studies of steroid molecular structures and the understanding of steroid structural-functional relationships. The structural data of these and other classes of bioactive molecules are being placed in the PROPHET system, a national computer network of the NIH Division of Research Resources, designed to aid in the correlation of structure with function in pharmacological and toxicological studies. Software has been developed in the PROPHET system to allow users with varied interests to tap the wealth of information contained in the structural data and to foster productive interdisciplinary collaborations in functional analysis.